Nanoscale friction at the quartz-quartz/kaolinite interface

The nanoscale friction behavior of quartz-quartz and quartz-kaolinite interfaces is investigated through Steered Molecular Dynamics (SMD) simulations. The effects of normal load, sliding velocity, temperature, and hydration on the friction behavior are discussed, and the friction mechanism of quartz and quartz/kaolinite interface is revealed. The friction coefficients of all systems at different cases are obtained and compared with other experimental results for validation. The simulation results show that the stick-slip effect in all interfaces was found during the friction process, where the higher the sliding velocity and hydration, or the lower the normal load, the weaker the stick-slip effect. The friction load increased with the rising normal load, and the relationship between shear stress and normal load was approximately linear. The friction coefficient and cohesion of the quartz-quartz interface could rise with the increasing sliding velocity or the decreasing temperature. Moreover, the friction coefficient of quartz-kaolinite was significantly smaller than that of quartz-quartz, indicating that the presence of clay could weaken the frictional strength of quartz. The effect of the interlayer water film on friction behavior was rather complex, showing the lubricating or bonding role, which has been discussed and analyzed in the present study.